\begin{tikzpicture}
    \pgfmathsetmacro{\a}{3}
    \pgfmathsetmacro{\b}{1.2}
    \pgfmathsetmacro{\c}{2}
    \pgfmathsetmacro{\d}{0.8}

    \begin{scope}
        \tkzDefPoints{0/0/A, \a/0/B, \a/\c/C, 0/\c/D}
        \tkzDrawPolygon(A,B,C,D)
        \tkzDrawSegments[dim={$a$,-10pt,}](A,B)
        \tkzDrawSegments[dim={$c$, 10pt,rotate=90}](A,D)
    \end{scope}

    \begin{scope}[xshift=4cm]
        \tkzDefPoints{0/0/A, \b/0/B, \b/\d/C, 0/\d/D}
        \tkzDrawPolygon(A,B,C,D)
        \tkzDrawSegments[dim={$b$,-10pt,}](A,B)
        \tkzDrawSegments[dim={$d$,-10pt,rotate=90}](B,C)
    \end{scope}
\end{tikzpicture}

